Pope Francis spoke during his visit to Ireland Saturday of his shame over the "appalling crimes" of historic child abuse in the Catholic Church and said outrage was justified.

(CNN) — A former Vatican ambassador to Washington has called for Pope Francis to resign over his handling of sexual abuse allegations against a prominent cardinal in 2013.

In a statement seen by CNN Sunday, former Archbishop Carlo Maria Vigano said he told the Pope about allegations of sexual abuse against high-profile American Cardinal Theodore McCarrick five years ago, but that the Pontiff did nothing about it.

McCarrick, 88, who once led the Archdiocese of Washington and was a force in American politics, resigned last month after a decades-old allegation of sexual abuse of a teenage altar boy. The Pope also ordered McCarrick’s’ suspension from public ministry.

“He [Pope Francis] knew from at least June 23, 2013 that McCarrick was a serial predator,” Vigano said in the lengthy statement dated August 22, adding, “although he knew that he was a corrupt man, he covered him to the bitter end.”

“It was only when he was forced by the report of the abuse of a minor, again on the basis of media attention, that he took action [regarding McCarrick] to save his image in the media,” Vigano continued.

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A source close to Vigano confirmed the letter is genuine. CNN has so far not received a response from the Vatican.

Vigano, who retired in 2016 at age 75, called for the Pontiff to resign over his failure to act. “Pope Francis must be the first to set a good example to Cardinals and Bishops who covered up McCarrick’s abuses and resign along with all of them,” he said.

Vigano also says Washington Cardinal Donald Wuerl was aware of reports of sexual abuse by his predecessor McCarrick.

“Cardinal Wuerl, well aware of the continuous abuses committed by Cardinal McCarrick and the sanctions imposed on him by Pope Benedict, transgressing the Pope’s order also allowed him to reside at a seminary in Washington D.C.,” said Vigano.

Edward McFadden, spokesperson for archdiocese of Washington, disputed the notion that Wuerl ignored allegations about McCarrick.

“In spite of what Archbishop Vigano’s memo claims, Cardinal Wuerl did not receive any documentation or information during his time in Washington regarding any actions taken against Archbishop McCarrick,” he said.

But the bishop of the Diocese of Tyler, Texas, told his parishioners he thinks McCarrick’s allegations are “credible.”

“Let us be clear that they are still allegations, but as your shepherd, I find them to be credible,” the Most Reverend Joseph E. Strickland wrote in a letter to members of the diocese.

Strickland’s letter did not say why he believes the allegations are credible. CNN has reached out to his office for explanation.

Vigano’s statement comes at a delicate time for Pope Francis, who is on a visit to Ireland where he has been grappling with the fallout of a Pennsylvania grand jury report into clerical sexual abuse spanning decades, while also meeting with survivors of Ireland’s own sex abuse scandal.

The Pennsylvania report found that more than 1,000 minors had been sexually abused by more than 300 Catholic priests over seven decades.

In an unusually blunt letter released by the Vatican last week, the Pope directly referred to the Pennsylvania report and acknowledged the Catholic Church’s failure to act, adding “we showed no care for the little ones; we abandoned them.”

On Saturday, the Pope again spoke in Dublin of his shame over the “appalling crimes” of historic child abuse in the Catholic Church and said outrage was justified, although he did not mention the Pennsylvania scandal specifically.

Meanwhile, Irish Prime Minister Leo Varadkar, who spoke ahead of the Pope on Saturday, did not skirt the current abuse revelations that have emerged in Pennsylvania.

“In recent weeks, we have all listened to heartbreaking stories from Pennsylvania of brutal crimes perpetrated by people within the Catholic Church, and then obscured to protect the institution at the expense of innocent victims,” he said. “It is a story all too tragically familiar here in Ireland.”

Pope Francis continues his 32-hour visit to Ireland with a Sunday Mass at Phoenix Park in Dublin, with around 500,000 people expected to attend. Thousands of people are also expected to take to the streets in protest.